COURSE of the MONTH

dtpicker control and format function

i have 2 questions
1- in the DTPicker control i set format to custom, and custom format to hh:mm:ss but when run the program all things is ok except one thing i want the hours to be from 00 to 23 not from 00 to 12 how can i do that?

2- i want to use the format function in order two represent any number in 4 characters only and leave blank (not 0) in the case of the number is less than 4 characters
e.g.